The major objectives are to determine the mechanisms by which the angiotensins and kinins are formed, exert their actions and are inactivated during circulation through two of their major target organs: the adrenal gland and the kidney. Formation of angiotensin II will be studied using synthetic angiotensin I labelled intrinsically with H3 and/or C14. Chemical identification of metabolites will be supplemented by biological and radioimmunoassays. The possible formation of bradykinin from one of its higher-homologs can be detected in the same way. The actions of the angiotensins and kinins will be studied by examining the relevance of solution structures to biological effects. Kinins and angiotensins and selected analogs and homologs will be synthesized and then characterized in terms of circular dichroism and nuclear magnetic resonance spectra and in terms of biological effects. We will continue to synthesize and characterize analogs in which side-chains are altered while peptide conformation is maintained to determine which residues function in direct interactions which receptors and which function to maintain the configuration of adjacent residues. Actions of the kinins and angiotensins will also be studied in terms of specific secretory products of the adrenal cortex and medulla and in terms of subcellular effects (e.g. exocytosis) observable by electron microscopy. Specific metabolic steps leading to the inactivation of bradykinin and angiotensin II will be studied using H3- and/or C14-labelled peptides in organ perfusions. Possible subcellular sites of the degradative enzymes will be studied by examination of thin sections and freeze-fracture replicas. Similarly, an antibody to the bradykininase/angiotensin I converting enzyme has been prepared. This antibody, conjugated to an EM marker such as microperoxidase, will be used to determine the occurrence and the subcellular sites of the enzyme.